ISO/TS 19159-4:2022 地理情報 — リモートセンシング画像センサーとデータのキャリブレーションと検証 — Part 4: 宇宙搭載パッシブマイクロ波放射計 | ページ 6

3.1

antenna beam width

half-power full width

half-power beam width

full angle at which the antenna's pattern (in power units) is at half its maximum value

Note 1 to entry: In engineering convention, this is also known as the"3 dB beam width."

3.2

antenna main-beam efficiency

η_M

fraction of the total radiant energy that is received from the main beam (3.29) , which is defined as the ratio of the power received within the"main lobe" to that of the total power received by the antenna

Note 2 to entry: Main beam (3.29) is also referred as main lobe.

3.3

antenna output temperature

T_A,out

physical temperature of correctional impedance that delivers to the receiver the same noise power as the antenna collects

where

	TA	is the antenna aperture temperature;
	Tp	is the physical temperature of the antenna;
		is the Ohmic loss;
	ηΩ	is the Ohmic efficiency of the antenna.

3.4

antenna pattern

ratio of the electronic-field strength radiated in the direction θ to that radiated in the beam-maximum direction

Note 1 to entry: In microwave radiometry, this is the spatial distribution of a quantity (usually proportional to or equal to power flux density or radiation intensity) that characterizes the electromagnetic field generated by an antenna.

[SOURCE:ISO/TS 19159-3:2018, 3.2, modified — Note 1 to entry added.]

3.5

antenna radiation efficiency

η_l

ratio of the total radiated power divided by the total power accepted by the antenna

Note 2 to entry: Antenna radiation efficiency (η_l ) is also called as Ohmic efficiency (η_Ω).

3.6

antenna sidelobe

antenna radiation pattern away from its main beam (3.29) , or defined as part of an antenna response pattern which is not contained in the main beam

3.7

antenna temperature

T_A

temperature (K) equivalent of the power received with an antenna, or physical temperature (K) of the ‘antenna radiation resistance’ that delivers to a matched receiver the same noise power as the antenna collects

3.8

attitude

orientation of a body, described by the angles between the axes of that body’s coordinate system and the axes of an external coordinate system

[SOURCE:ISO 19116:2019, 3.3, modified — Note 1 to entry removed.]

3.9

blackbody load

microwave load with characteristics very close to those of a perfect blackbody (3.30) within a certain frequency range

3.10

blackbody radiance

I_bb,v

Note 1 to entry: The constants are defined in terms of a perfect blackbody (3.30) .

3.11

boresight

calibration of a lidar sensor system, equipped with an inertial measurement unit (IMU) and a global navigation satellite system (GNSS), to accurately determine or establish its position and orientation

Note 1 to entry: In microwave radiometry, the boresight is usually used to characterize the beam-maximum direction of a highly directive antenna.

[SOURCE:ISO/TS 19159-2:2016, 4.4, modified — Original note 1 to entry deleted and replaced with new note 1 to entry.]

3.12

brightness temperature

T_B

descriptive measure of radiation in terms of the temperature (K) of a hypothetical blackbody emitting an identical amount of radiation at the same wavelength, which can be derived from the Planck's radiation law

Note 1 to entry: In the Rayleigh-Jeans limit, the microwave power per unit bandwidth received by a radiometer, P, (3.33) is:

Note 2 to entry:P=k·T_B

Note 3 to entry: where k is the Boltzmann’s constant (k= 1.380 648 52×10^-23 J/K).

where

		is the Rayleigh–Jeans equivalent brightness temperature;
	v	is the frequency in Hz;
	c	is the velocity of light (2.997 925×108m/s);
	k	is the Boltzmann’s constant (1.380 648 52×10-23 J/K);
	Iv	is the radiance.

3.13

brightness temperature sensitivity

minimum detectable change of the brightness temperature (3.12) incident at the antenna-collecting aperture

Note 1 to entry: For the purpose of this document, the noise equivalent delta temperature (NEDT) values shall be defined as the standard deviation of the radiometer (3.33) output in K when the antenna is viewing a 300 K uniform and stable target. For microwave radiometer, this is also called radiometric resolution (3.34) .

Note 2 to entry: The formula relative to sensitivity is shown in D.2.

3.14

calibration

process of quantitatively defining a system’s response to known, controlled signal inputs

[SOURCE:ISO/TS 19101-2:2018, 3.2]

3.15

calibration equation

equation relating the primary measure and that of the radiometer (3.33) , for example the brightness temperature (3.12) , to subsidiary measurands, such as powers, and to calibration quantities, such as standard values

3.16

co-polarization

fraction of total power within the main beam (3.29) that is detected in the main polarization (3.31)

3.17

cosmic microwave background

CMB

isotropic radiation in the microwave region that is observed almost completely uniformly in all directions

Note 1 to entry: This radiation is understood to be the radiation emitted by the universe at an early period of its history.

3.18

cross-calibration

process of relating the measurements of one instrument to another instrument which is usually well-calibrated, serving as a reference

Note 1 to entry: Cross-calibration of instruments operating during the same period requires careful collocation wherein instrument outputs are compared when the instruments are viewing the same Earth scenes, at the same times, from the same viewing angles.

3.19

cross-polarization

fraction of total power within the main beam that is detected in the orthogonal polarization

3.20

effective blackbody brightness temperature

physical temperature of a perfect absorber that would produce the same spectral brightness density or spectral radiance density as that under consideration

3.21

emissivity

ratio of the energy radiated by an emissive surface relative to that of an ideal blackbody source at the same temperature

3.22

end-to-end calibration

<of microwave radiometer> calibration of the entire radiometer (3.33) system as a unit, achieved by observing the values of output quantities (e.g. voltage, power) for known values of incident radiance at the antenna aperture

3.23

experimental standard deviation

for a series of n measurements of the same measurand, the quantity, s(q_k ), characterizing the dispersion of the results and given by the formula

where

	qk	is the result of the kth measurement;
		is the arithmetic mean of the n results considered;
	n	is the number of the measurements.

Note 1 to entry: Considering the series of n values as a sample of a distribution, and is called the experimental standard deviation of the mean.

[SOURCE:ISO/IEC Guide 98-3:2008 B.2.17, modified — Notes 3 and 4 to entry have been removed.]

3.24

external calibration

calibration method that applies reference signals from targets that lie outside the radiometer (3.33)

Note 1 to entry: If these targets illuminate the antenna of the radiometer, an end-to-end calibration (3.22) is obtained.

3.25

half-power bandwidth

frequency range at which the power response is half the maximum value

3.26

incident angle

vertical angle between the line from the detected element to the sensor and the local surface normal (tangent plane normal)

[SOURCE:ISO/TS 19130-1:2018, 3.13]

3.27

instantaneous field of view

IFOV

instantaneous region seen by a single detector element, measured in angular space

[SOURCE:ISO/TS 19130-2:2014, 4.36, modified — Admitted term added.]

3.28

linearity

property of a mathematical relationship or function which means that it can be graphically represented as a straight line

Note 1 to entry: The formula relative to the linearity is shown in D.1.

3.29

main beam

main lobe

major part of the radiated field where maximum radiated energy exists (region around the direction of maximum radiation)

Note 1 to entry: The main beam is also defined as 2.5 times 3 dB beamwidth for mathematical computation of antenna main beam efficiency.

Note 2 to entry: The width of main beam (which is commonly called"null to null beamwidth") is defined as the angular span between the first pattern nulls (the magnitude of the radiation pattern decreases to zero, negative infinity dB) adjacent to the main lobes.

3.30

perfect blackbody

3.31

polarization

restricting radiation, especially light, vibrations to a single plane

Note 1 to entry: In microwave radiometry, the direction of the polarization is defined by the direction of the electric field (E, in most cases) or magnetic field (H) in a propagating electromagnetic wave.

Note 2 to entry: A general, elliptically polarized electromagnetic plane wave propagating in the direction can have its electric field expressed in phasor form as:

where

		are unit vectors oriented perpendicular to ;
	Ep and Eq	are the complex amplitudes of the electric field in the directions, respectively;
	wn	is the wavenumber of the propagating wave, and .

Note 3 to entry: Vertical polarization and horizontal polarization are specific cases of elliptical polarization.

[SOURCE:ISO 19115-2:2019, 3.24, modified — Notes to entry added.]

3.32

radiance

I_v

point on a surface and in a given direction, the radiant intensity of an element of the surface, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction

where

	dP	is the differential radiation power;
	dΩ	is the differential solid angle;
		in which is the angle between the direction defined by the solid angle and the normal to the area element da.

3.33

radiometer

very sensitive receiver, typically with an antenna input, used to measure radiated electromagnetic power

3.34

radiometric resolution

smallest change in input brightness temperature (3.12) or radiance (3.32) that can be detected in the system output

where

		is the radiometric resolution;
		is the radiometer system temperature;
	B	is the bandwidth of the radiometer system;
		is the integral time.

Radiometric resolution can be also estimated from the variant of this equation that is appropriate for the particular radiometer (3.33) in question.

3.35

spatial resolution

length of the major and/or minor axes diameters of the 3 dB contour of the antenna pattern (3.4) projected onto the Earth’s surface

Note 1 to entry: The diameter of the two axes may differ.

Note 2 to entry: See also IFOV (3.27).

3.36

spectral response function

SRF

relative sensitivity of the sensor to monochromatic radiation of different wavelengths

where

		is the output voltage difference;
		is the input power difference;
	v	is the frequency in Hz.

3.37

spillover

condition where radiation from the feed antenna falls outside the edge of the dish and does not contribute to the main beam (3.29)

where

		is the co-polarization antenna pattern;
		is the cross-polarization antenna pattern;
	dΩ	is the differential solid angle;
	Z	is the Earth.

3.38

stability

ability of a measuring instrument or measuring system to maintain its metrological characteristics constant with time

3.39

Stokes parameters

set of four real quantities, which completely describe the polarization (3.31) state of monochromatic or quasi-monochromatic radiation

Note 1 to entry: The parameters are, collectively, known as the Stokes Real{ordered}, a 4 × 1 Real{ordered}.

>where T_v, T_h, T₃ and T₄ are, respectively, the vertically and horizontally polarized and the third and fourth Stokes parameters, and B is the radiometer system bandwidth.

[SOURCE:ISO 12005:2003, 3.11, modified — Original notes to entry have been removed and replaced.]

3.40

traceability chain

sequence of measurement standards and calibrations (3.14) that is used to relate a measurement result to a reference

[SOURCE:ISO/IEC Guide 99:2007, 2.42, modified — Notes to entry have been removed.]

3.41

true value

value consistent with the definition of a given quantity

Note 1 to entry: This is a value that would be obtained by perfect measurement. However, this value is in principle and in practice unknowable.

[SOURCE:ISO 17123-1:2014, 3.1.3]

3.42

two-point calibration

adjustment of the relationship between the input signal and the output response of a radiometer (3.33) using two distinct input stimuli

Note 1 to entry: Assuming a linear receiver, all possible input signal levels can now be retrieved from the radiometer output responses.

Note 2 to entry: In the case of an external end-to-end calibration (3.22) , the input signal equals the antenna temperature (3.7) of the radiometer.

3.43

uncertainty

parameter, associated with the result of measurement, that characterizes the dispersion of values that could reasonably be attributed to the measurand

Note 1 to entry: When the quality of accuracy or precision of measured values, such as coordinates, is to be characterized quantitatively, the quality parameter is an estimate of the uncertainty of the measurement results. Because accuracy is a qualitative concept, one should not use it quantitatively, that is, associate numbers with it; numbers should be associated with measures of uncertainty instead.

[SOURCE:ISO 19116:2019, 3.28]

3.44

validation

process of assessing, by independent means, the quality of the data products derived from the system outputs

Note 1 to entry: In this document, the term validation is used in a limited sense and only relates to the validation of calibration data in order to control their change over time.

[SOURCE:ISO 19101-2:2018, 3.41, modified — Note 1 to entry added.]

3.45

viewing angle

angle between the line-of-sight and the line orthogonal to the surface of the display at the point where the line-of-sight intersects the image surface of the display

[SOURCE:ISO 9241-5:1998, 3.1]

3.46

vicarious calibration

post-launch calibration of sensors that make use of natural or artificial sites on the surface of the Earth

[SOURCE:ISO/TS 19159-1:2014, 4.41]